【笔记】Eclipse and Java for Total Beginners—009

Lesson 09 – MyLibrary Class and ArrayList

• How can we hold books, etc. in a collection?
• MyLibrary object to hold Person & Entry objects
• Introduce ArrayList in scrapbook
• Introduce Java Generics
• Method chaining

使用ArrayList前，要添加java.util.

  
    

   
      1 
   
     ArrayList
   
     <
   
     Book
   
     >
   
      list 
   
     =
   
      
   
     new
   
      ArrayList
   
     <
   
     Book
   
     >
   
     ();

   
      2 
   
     

   
      3 
   
     Book b1 
   
     =
   
      
   
     new
   
      Book(
   
     "
   
     Great Expectations
   
     "
   
     );

   
      4 
   
     Book b2 
   
     =
   
      
   
     new
   
      Book(
   
     "
   
     War and Peace
   
     "
   
     );

   
      5 
   
     list.add(b1);

   
      6 
   
     list.add(b2);

   
      7 
   
     

   
      8 
   
     Person p1 
   
     =
   
      
   
     new
   
      Person();

   
      9 
   
     p1.setName(
   
     "
   
     Fred
   
     "
   
     );

   
     10 
   
     b1.setPerson(p1);

   
     11 
   
     

   
     12 
   
     list.get(
   
     0
   
     ).getPerson().getName();

   
     13 
   
     

   
     14 
   
     list.remmove(b1);

   
     15 
   
     list
  
    

问题：Inspect提示：

Book cannot be resolved to a type
Book cannot be resolved to a type
Book cannot be resolved to a type
Book cannot be resolved to a type
Book cannot be resolved to a type
Book cannot be resolved to a type

问题解决方法：

1> 在编辑代码时输入new后，按ALT+/ 自动补齐，无反应。

     windows / preferences / Java / Editor / Templates / 选new / Edit / 勾选 Automatically insert / 在context里选 Java。

2>Book cannot be resolved to a type，添加Book

    1) Click the "Set Import Declarations" button right next to red square "Stop evaluation" button.

    2) Select "org.totalbeginner.tutorial* "-> click the "Add Type" button  

    3) Search for class 'Book' and 'Person' and add them to your MyScrapbook.jpage

小结：

　　在上面的代码里，用ArrayList列出了Library Class的特性，用Scrapbook验证时，可灵活调用各种方法，比如，根据Book对象去查询：

      list.indexOf(b2);

     或是由书查读者：

      list.get(0).getPerson().getName();